Are silt and clay considered poor substrates in protected areas due to being nutrient-rich?

Silt and clay are often regarded as poor substrates in protected areas not primarily because they are nutrient-rich, but because of their physical properties that can affect aquatic ecosystems. In these areas, silt and clay can lead to reduced water flow and can trap organic matter and detritus, which may create anoxic conditions that are unfavorable for many aquatic organisms. This substrate can also hinder the growth of rooted aquatic vegetation, which is essential for habitat complexity and food web dynamics.

The nutrient-rich nature of silt and clay can contribute to eutrophication when excessive nutrients promote algal blooms, but this nutrient aspect doesn't necessarily make them a good substrate in the context of supporting diverse aquatic life. In many cases, a substrate that promotes healthy vegetation and provides habitat tends to be sandy or gravelly, which allows for better water circulation and root growth. Thus, the determination of poor substrates in protected areas is more closely tied to their physical effects on ecosystem health rather than simply their nutrient content.